Commit 6dd761d9 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: guest_memfd: make kvm_gmem_prepare_folio() operate on a single struct kvm 



This is now possible because preparation is done by kvm_gmem_get_pfn()
instead of fallocate().  In practice this is not a limitation, because
even though guest_memfd can be bound to multiple struct kvm, for
hardware implementations of confidential computing only one guest
(identified by an ASID on SEV-SNP, or an HKID on TDX) will be able
to access it.

In the case of intra-host migration (not implemented yet for SEV-SNP,
but we can use SEV-ES as an idea of how it will work), the new struct
kvm inherits the same ASID and preparation need not be repeated.

Reviewed-by: default avatarMichael Roth <michael.roth@amd.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent b8552431

virt/kvm/guest_memfd.c

+19 −30
Original line number Diff line number Diff line
@@ -25,37 +25,27 @@ static inline kvm_pfn_t folio_file_pfn(struct folio *folio, pgoff_t index) 
	return folio_pfn(folio) + (index & (folio_nr_pages(folio) - 1));

}



static int __kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct folio *folio)

static int __kvm_gmem_prepare_folio(struct kvm *kvm, struct kvm_memory_slot *slot,

				    pgoff_t index, struct folio *folio)

{

#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE

	struct list_head *gmem_list = &inode->i_mapping->i_private_list;

	struct kvm_gmem *gmem;



	list_for_each_entry(gmem, gmem_list, entry) {

		struct kvm_memory_slot *slot;

		struct kvm *kvm = gmem->kvm;

	kvm_pfn_t pfn;

	gfn_t gfn;

	int rc;



	if (!kvm_arch_gmem_prepare_needed(kvm))

			continue;



		slot = xa_load(&gmem->bindings, index);

		if (!slot)

			continue;

		return 0;



	pfn = folio_file_pfn(folio, index);

	gfn = slot->base_gfn + index - slot->gmem.pgoff;

	rc = kvm_arch_gmem_prepare(kvm, gfn, pfn, folio_order(folio));

	if (rc) {

			pr_warn_ratelimited("gmem: Failed to prepare folio for GFN %llx PFN %llx error %d.\n",

					    gfn, pfn, rc);

		pr_warn_ratelimited("gmem: Failed to prepare folio for index %lx GFN %llx PFN %llx error %d.\n",

				    index, gfn, pfn, rc);

		return rc;

	}

	}



#endif



	return 0;

}
@@ -65,7 +55,7 @@ static int __kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct f 
 * On successful return the guest sees a zero page so as to avoid

 * leaking host data and the up-to-date flag is set.

 */

static int kvm_gmem_prepare_folio(struct file *file, struct kvm_memory_slot *slot,

static int kvm_gmem_prepare_folio(struct kvm *kvm, struct kvm_memory_slot *slot,

				  gfn_t gfn, struct folio *folio)

{

	unsigned long nr_pages, i;
@@ -95,8 +85,7 @@ static int kvm_gmem_prepare_folio(struct file *file, struct kvm_memory_slot *slo 
	WARN_ON(!IS_ALIGNED(slot->gmem.pgoff, 1 << folio_order(folio)));

	index = gfn - slot->base_gfn + slot->gmem.pgoff;

	index = ALIGN_DOWN(index, 1 << folio_order(folio));



	r = __kvm_gmem_prepare_folio(file_inode(file), index, folio);

	r = __kvm_gmem_prepare_folio(kvm, slot, index, folio);

	if (!r)

		folio_mark_uptodate(folio);
@@ -619,7 +608,7 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, 
		goto out;

	}



	r = kvm_gmem_prepare_folio(file, slot, gfn, folio);

	r = kvm_gmem_prepare_folio(kvm, slot, gfn, folio);

	folio_unlock(folio);

	if (r < 0)

		folio_put(folio);